The present invention relates generally to induction heating cooking apparatus, and in particular to a detecting circuit for detecting improper placement of a utensil load with respect to an induction heating coil with which the load is electromagnetically coupled to generate heat.
Induction heating cooking apparatus usually comprises an inverter and an induction heating coil of a flat, spiral configuration mounted below a cook top. The coil is energized by ultrasonic frequency energy provided by the inverter to generate a time-varying magnetic field. When a utensil of proper size and material is symmetrically placed with respect to the center of the heating coil, i.e. the center of utensil bottom coinciding the center of heating coil, electromagnetic coupling between the heating coil and the utensil is at a maximum so that a maximum amount of heat is generated in the utensil. Although the cook top surface is usually marked with radial lines indicating the proper location of utensil for maximum power delivery thereto, the utensil is often displaced from the marked area resulting in a loss of power and a leakage of magnetic flux which causes radio interference.